Tag some "new Binder()" instances to detect leaks.

We've seen evidence of a Binder leak, and our hunch is that it's
caused by one of these anonymous "new Binder()" sites.  Adding
descriptors will help us identify the leak cause.

Bug: 192415943
Test: atest BluetoothInstrumentationTests
Change-Id: I30cd15f084cf50f67edd833b27b853c4b22e1db1